40.What does the second paragraph mainly discuss?

(A)The Milky Way

(B)Major categories of galaxies

(C)How elliptical galaxies are formed

(D)Differences between irregular and spiral galaxies

41.The word "which"in line 7refers to

(A)dust

(B)gas

(C)pattern

(D)galaxy

42.According to the passage,new stars are formed in spiral galaxies due to

(A)an explosion of gas

(B)the compression of gas and dust

(C)the combining of old stars

(D)strong radio emissions

43.The word "symmetrical"in line 9is closest in meaning to

(A)proportionally balanced

(B)commonly seen

(C)typically large

(D)steadily growing

44.The word "obvious"in line 10is closest in meaning to

(A)discovered

(B)apparent

(C)understood

(D)simplistic

45.According to the passage,which of the following is NOT true of elliptical galaxies?

(A)They are the largest galaxies.

(B)They mostly contain old stars.

(C)They contain a high amount of interstellar gas.

(D)They have a spherical shape.

46.Which of the following characteristics of radio galaxies is mentioned in the passage?

(A)They are a type of elliptical galaxy.

(B)They are usually too small to be seen with a telescope.

(C)They are closely related to irregular galaxies.

(D)They are not as bright as spiral galaxies.

47.What percentage of galaxies are irregular?

(A)10%

(B)25%

(C)50%

(D)75%

48.The word "they"in line 21refers to

(A)intervals

(B)yardsticks

(C)distances

(D)galaxies

49.Why does the author mention the Virgo galaxy and the Andromeda galaxy in the third paragraph?

(A)To describe the effect that distance has no visibility.

(B)To compare the ages of two relatively young galaxies.

(C)To emphasize the vast distances of the galaxies from Earth.

(D)To explain why certain galaxies cannot be seen by a telescope.

50.The word "dominated"in line 26is closest in meaning to

(A)threatened

(B)replaced

(C)were developing in

(D)were prevalent in